Field of Invention
The present invention relates to a technical field of textile, and more particularly to method and apparatus for producing ultra-smooth knitted fabric using hairy yarn.
Description of Related Arts
Weft knitting produces a knitted fabric using one or several yarns simultaneously and laterally along a fabric to form loops which interlock with each other longitudinally by needles, wherein weft knitting is divided into the single-sided and the double-sided. Weft knitted fabric forming process is divided into three stages: yarn feeding, wherein yarn is fed into a forming area of a weft knitting machine with a constant tension; knitting, wherein the yarn in the forming area is processed with different loop-forming methods to convert into the weft knitted fabrics; and up-taking, wherein the weft knitted fabrics are reeled from the loop-forming area to form a fabric package with a certain tension. The weft knitting machine commonly comprises circular arranged knitting needles, which is called a circular machine or known as a knitting machine using crochet hooks or latch needles as the key parts of loop-forming and cone yarn as the feeding material. The cone yarn is formed by winding bobbin yarns onto a cone package. Modern winding process is characterized by high speed and automation, wherein an automatic winding speed can be up to 1200 m/min, leading to serious problems of yarn during winding. In practice, it is noticed that after automatic winding, bobbin yarn total hair amount are increased by 3-6 times, wherein the hairs equal to or longer than 4 mm present higher increase amplitudes. Cone yarn with excessive long hairs will lower resultant fabric appearance due to entanglements of hairs to form yarn imperfections such as thick places, neps. Furthermore, long hairs of cone yarn are easily wrapped or wounded onto the knitting needles to break or even destruct them, reducing knitting efficiency dramatically.
For solving the above problems caused by yarn hairiness, current solutions are: improving weft knitting yarn hairiness property, and improving weft knitting processes as well as technologies; wherein improvement of weft knitting yarn hairiness property mainly solves the problem that yarn hairiness is over-increased during winding. Although it is possible to solve the problem by singeing of yarn, the singeing of yarn leads to fiber material losses and wastes. With rising costs of fiber materials, manufacturers are not likely to adapt singeing. Winding process optimization can partly suppress yarn hairiness increase by grinding and waxing, but employing hairiness reducing devices during winding are considered effective methods to solve yarn hairiness problems. There are a lot of relevant patents for the effective methods; however they are with similar principles, wherein in a winding machine, a forward-moving yarn is just roughly treated by one-step false-twisting method or one-step vortex rotating method; in such a manner that yarn hairs can be partly reduced by re-winding them onto yarn surface. Representatively, European patent EP 0,866,014 A2, published Sep. 23, 1998, Auto Winder, discloses mechanical action of false-twisting disc during winding, which forces free protruding fiber ends to return to a yarn body along a twisting direction, so as to reduce the yarn hairiness. U.S. Pat. No. 6,374,588 B1, published Apr. 23, 2002, Hairiness controlling device and winder, discloses mechanical action of false-twisting disc during winding, which forces free protruding fiber ends to return to a yarn body along a twisting direction, so as to reduce the yarn hairiness. European patent EP 1,146,002 A2, published Oct. 17, 2001, Automatic winder and hairiness suppressing device, discloses using an air vortex tube, so as to generate rotary airflow to re-wrap hairiness onto yarn body to reduce hairiness. In principle, airflow alone is not able to provide a sufficient wrapping effect. European patent EP 1,013,803 A2, published Jun. 28, 2000, Hairiness suppressing device for automatic winder, also discloses using an air vortex tube, which rotates yarn with airflow. When the rotating yarn passes through a regulating plate, fibers wrap onto a yarn body, in order to reduce hairiness. Chinese patent ZL99127507.1, published Jul. 5, 2000, Hairiness suppressing device for automatic winder, also discloses using an air vortex tube, which rotates yarn with airflow. However, two controller are provided at both ends of the device for ensuring yarn rotates along an axis thereof and causes a false-twisting effect, improving efficiency of reducing yarn hairiness. In addition, Chinese patent ZL 200710052991.8, published Jan. 23, 2008, Method to reduce yarn hairiness, discloses false-twisting ironing method, which attaches yarn and wraps yarn hairiness during winding; however a very small amount of the hairiness is involved into a yarn body, so as to reduce the yarn hairiness during winding and knitting. Above methods and devices for reducing yarn hairiness have common functions: only suppressing the amount increase of yarn hairs by flattening or re-wrapping them onto yarn stem via airflow or mechanical force. Practical applications show that the flattened or re-wrapped hairiness has three defects: firstly, the hairiness flattening or re-wrapping direction is opposite to the moving direction of yarn as it is winded to form a cone package, then the flattened or re-wrapped hairiness is directional to the moving of yarn as it is un-winded from the cone package during weft-knitting process, in which the flattened or re-wrapped hairiness is extremely easy to be scraped or bounced out; secondly, throughout flattening or re-wrapping process, the yarn hairiness lacks of positive and effective nipping force to improve the surface structure compactness, leading to a loose flattened or wrapped structure which facilitates the hairiness reformation of yarn enduring friction or rubbing again; thirdly, yarn imperfections such as neps and thick places are largely increased due to the fiber concentrations when the hairiness roughly flattened or re-wrapped onto yarn stem. To solve the problem, Chinese Patent ZL 201410204503.0, published May 15, 2014, Method for improving yarn surface structure with positively holding, discloses wrapping yarn surface hairiness tightly on a yarn stem by a negative pressure holding. It is proved by practice that the method is able to effectively improve the hair-wrapping tightness. However, technical problems are still not solved such as the hairiness wrapping direction opposite to the yarn moving direction, yarn imperfection formation due to the rough wrapping hairiness concentrations. Moreover, above conventional hairiness reduction devices are not able to solve the hairiness problem at a room temperature for spun yarn of highly resilient fibers (such as wool fibers) and high stiffness fibers (such as hemp fibers).
Currently, there are two main methods for improving weft knitting techniques and technologies. Firstly, weft knitting processes simply employ the yarn hairiness reduction techniques and devices which are commonly used for winding process. However, many fatal technical problems still exist: the hairiness reduction techniques and devices only partly decrease yarn hairiness, instead of eliminating yarn hairiness thoroughly; the remaining hair ends in knitted fabric facilitates the decreased hairiness greatly protruding out of fabric surface again after repeated washing, scouring and bleaching. Disappointedly, after introducing and grafting the above techniques, such problems as hairiness wrapping direction, thorough hairiness elimination and yarn increased imperfections due to fiber concentration are still unsolved. Thus, ultra-smooth weft knitting using hairy cone yarn is impossible by simply employing the hairiness reducing techniques and devices for yarn winding processes. The second method is using weft knitting processes optimization to improve the weft-knitting quality such as reducing friction by waxing, eliminating static electricity by wetting, and setting yarn by steaming; Obviously, the second method only improves the weft knitting from aspects such as friction reduction, heat setting, and static electricity elimination, which is not directly aimed to solve those weft knitting problems caused by the yarn surface hairiness, and is not able to achieve the ultra-smooth weft knitting production of hairy yarn.